Changing Land-Atmosphere Feedbacks in Tropical African Wetlands

拟议研究的主要目的是量化热带非洲湿地和气候之间的反馈。我们将通过在地球系统模型中实施动态湿地淹没计划来实现这一目标，并根据通过远程地球观测获得的土壤湿度，云量和甲烷（CH 4）浓度数据对该模型进行测试。我们的研究将解决以下关键问题：热带湿地的存在如何影响区域尺度的降雨？湿地CH 4排放是否强烈依赖于季节和年际水文变化？在环境和气候变化情景下，湿地的季节性和相关的甲烷排放将如何改变？这里提议的研究将以陆地表面建模和地球观测方面的最新发展为基础，将对湿地功能的详细水文理解纳入气候模型。我们将结合联合收割机新的卫星地球观测，实地测量，湿地淹没的新的动态表示大大增加了我们的湿地在地球系统的重要性的理解下的环境变化的情况。湿地以两种方式与气候系统相互作用。首先，它们控制着地表的热量和水分的流动，而这些热量和水分的流动可以反馈到当地和区域尺度上的降雨。其次，湿地通过缺氧降解有机物释放甲烷，形成水文和碳循环之间的关键环节。据估计，湿地甲烷排放量占全球甲烷预算的20-40%，使湿地成为大气甲烷的最大单一自然来源。预计CH 4和水文反馈在热带地区最活跃，但正是在这里，CH 4通量最不好量化。在气候变化的背景下，这些担忧被放大了：大气CO2浓度加倍导致的变暖可能会导致湿地CH 4排放量增加78%，其中大部分来自热带地区。此外，最近全球甲烷浓度的迅速增加被归因于热带湿地洪水泛滥程度的自然变化。由于缺乏关于热带湿地如何调节热量、水和微量气体向大气的流动的可靠资料，目前阻碍了在预测全球环境变化影响方面取得进展。我们迫切需要更好地了解湿地在地球系统中的功能。

The primary aim of the proposed research is to quantify the feedbacks between tropical African wetlands and climate. We will do this by implementing a dynamic wetland inundation scheme in an Earth system model, and test this model against soil moisture, cloud cover and methane (CH4) concentration data obtained through remote Earth observation. Our research will address the following key questions: How does the presence of tropical wetlands affect rainfall at the regional scale? Are wetland emissions of CH4 strongly dependent on seasonal and inter-annual hydrological variability? How will wetland seasonality and associated emissions of CH4 alter under environmental and climate change scenarios? The research proposed here will build on recent developments in land-surface modelling and Earth observation to incorporate detailed hydrological understanding of wetland function into climate models. We will combine novel satellite Earth observations, field measurements, and a new dynamical representation of wetland inundation to add greatly to our understanding of the importance of wetlands in the Earth system under scenarios of environmental change. Wetlands interact with the climate system in two ways. First, they govern the fluxes of heat and water at the land-surface, which can feed back on rainfall at the local and regional scales. Second, wetlands form a key link between the hydrological and carbon cycles, via anoxic degradation of organic matter to release CH4. It is estimated that wetland CH4 emissions represent 20-40% of the global CH4 budget making wetlands the largest single natural source of atmospheric CH4. Both CH4 and hydrological feedbacks are expected to be most active in the tropics, yet it is here that CH4 fluxes are least well quantified. These concerns are amplified in the context of climate change: warming resulting from a doubling of atmospheric CO2 concentrations will likely lead to a 78% increase in wetland emissions of CH4, most of which will come from tropical regions. Moreover, recent rapid increases in global CH4 concentrations have recently been attributed to natural variations in the extent of flooding in tropical wetlands. The lack of robust information on the ways in which tropical wetlands modulate fluxes of heat, water and trace gases to the atmosphere currently hampers progress in predicting the effects of global environmental change. We urgently need a better understanding of how wetlands function in the Earth system.